what is the structure of capacitor?

Capacitors are common electronic components in electronic equipment. The following briefly introduces the structure and characteristics of several common capacitors for reference.

run capacitor: It is made up of an aluminum cylinder as a negative electrode, and there is a liquid electrolyte inside, and a bent aluminum strip as a positive electrode. It also needs to be treated by DC voltage to form an oxide film on the positive electrode sheet as a medium. It is characterized by large capacity, but it is with large leakage, poor stability and positive and negative polarity, suitable for power supply filtering or low frequency circuits. When used, the positive and negative poles should not be reversed.

    Tantalum electrolytic start capacitor: It uses metal tantalum or niobium as the positive electrode, it use dilute sulfuric acid or the like as the negative electrode, and is made of the oxide film formed on the surface of tantalum or niobium. Its characteristics are: small size, large capacity, stable performance and long life. The insulation resistance is large. it has good temperature performance and it is used in equipment with high requirements.

    Ceramic capacitors: Ceramics are used as the medium. A silver layer is sprayed on both sides of the ceramic substrate, and then fired into a silver film as a plate. Its characteristics are: small size, good heat resistance, low loss, high insulation resistance, but small capacity, suitable for high frequency circuits. Ferroelectric ceramic capacitors have large capacity, but the loss and temperature coefficient are large, which is suitable for low frequency circuits.

    Mica capacitor: The electrode plate is sprayed with a metal foil or a silver layer on a mica plate. The plate and the mica are laminated one by one, and then die-cast in bakelite powder or sealed in epoxy resin. Its characteristics are: low dielectric loss and large insulation resistance. it has small temperature coefficient, so it is suitable for high frequency circuits.

    Film capacitor: The structure is the same as the paper capacitor, and the medium is polyester or polystyrene. Polyester film capacitor, it is with high dielectric constant, small size, large capacity, good stability, so it is suitable for bypass capacitors. Polystyrene film capacitors have low dielectric loss and high insulation resistance, but have a large temperature coefficient,so it can be used in high frequency circuits.

    Paper capacitor: Two pieces of metal foil are used as electrodes, sandwiched in extremely thin capacitor paper, rolled into a cylindrical or flat cylindrical core, and then sealed in a metal shell or an insulating material shell. It is characterized by a small size and a large capacity. However, the inherent inductance and loss are relatively large, which is suitable for low frequency circuits.

Metallized paper capacitor: The structure is basically the same as the paper capacitor. It is coated with a metal film on the capacitor paper to replace the metal foil. It is small in size and large in capacitance. It is generally used in low frequency circuits.

Oil-impregnated paper capacitor: It immerses the paper capacitor in a specially treated oil to enhance its withstand voltage. It is characterized by large capacitance and high pressure resistance, but it is bulky.